The invention relates to a motor vehicle with a hybrid drive, which includes a combustion engine, an electric machine operable as a motor and usable for starting the combustion engine, a controller and a starter usable for starting the engine. The invention also relates to a method for selecting an electric machine and/or a starter for starting a combustion engine in a motor vehicle having a hybrid drive.
Vehicles equipped with a hybrid drive and having both a combustion engine and an electric traction machine are well known in the art and advantageous due to their energy-saving mode of operation. Unlike motor vehicles equipped only with combustion engines, motor vehicles with hybrid vehicles are known in which the combustion engines are started with the electric machine via a drag and/or pulse start. For example, in a drag start, the separating clutch between the combustion engine and the electric machine is briefly engaged so that the electric machine “drags” the motor. Conversely, in a pulse start, the speed of the electric motor is usually briefly increased so as to transfer this “pulse” to the combustion engine after engaging the clutch and to bring the combustion engine to the correct firing position. However, mixed forms of these two types are also possible.
When the combustion engine is running, it is known in many hybrid vehicles to configure the electric machine so as to operate also as a generator, i.e., the electric machine can be used both as a motor and as a generator.
Disadvantageously, drag and/or pulse starts of the combustion engine with the electric traction machine require a complex control system to prevent jerking at the start-up. In addition, torques must be continuously provided, for example, to switch on the combustion engine even when with significant acceleration is provided by the electric machine. DE 103 46 919 A1 describes a hybrid vehicle which should allow to start a combustion engine in an emergency, for example, when the high-voltage battery operating the electric machine has a very low charge state. For this purpose, a starter motor powered by a low voltage of typically 12 V is provided. When the battery or the battery unit of the system with the higher voltage is insufficiently charged, but the low-voltage battery of 12 V is sufficiently charged, the starter motor can be used with the 12 V battery to start the combustion engine.
However, this cannot get around the aforedescribed disadvantages.